Semester 2 - GI infections Flashcards
How does peristalsis act as a barrier to infection?
Inhibits adherence, colonization of pathogenic microorganisms, constant flushing action
What are the physical barriers to infection in the GI tract?
Peristalsis and flow of liquids through the GI tract.
pH
Mucus
(Epithelial cell turnover in GIT?)
How does pH act as a barrier to infection?
Inhibits the growth of pathogenic microorganisms
Determines microbial blor in various areas of the GIT
How does mucus act as a barrier to infection?
Aids in flushing action
Provides a barrier to susceptible cells
Contains immune cells, antimicrobial peptides etc
What are some innate immune defenses found in the mucosa?
GALT
Peyer’s patches in SI
M cells (sample and deliver antigens to basolateral APCs)
Defensins (b-defensin, lysozyme, anti-microbial peptides AMPs etc)
How does GI flora contribute as a barrier to infection?
Inhibits the growth of pathogenic bacteria
Support the growth of other beneficial bacteria
Aid in digestion
What are the factors influencing susceptibility to GI infection?
Anatomical/mechanical: any obstruction to flow
Acidity: Changes to pH affect growth of flora, pathogens
GI flora: change in growth/composition of normal flora, pH, antibiotic use, diet etc
Immune composition: peyer’s patches inflammation
What are some sources of GI infection?
Fecal-oral transmission - stability of pathogens (food, water, person-to-person)
Hematogenous spread from a primary site (rare)
Bacterial, viral, parasitic
What is gastroenteritis?
Inflammation in bowel movement, increased looseness of stool
Dehydration, electrolyte loss
What is diarrhea?
Increase in bowel movements, increased looseness of stool
Dehydration, electrolyte loss
What is dysentery?
Infection and inflammation of the large intestine. Associated with blood and pus in feces, abdominal pain and cramping
What is enterocolitis
Inflammation of the small and large intestine
Abdominal bloating, bloody stool, constant urge to have a bowel movement
What is enteric fever (typhoid/paratyphoid)?
Fever, headache, malaise, anorexia
Hepatosplenomegaly, transient rash on trunk
May lead to intestinal perforation, hemorhage
What is a food borne illness?
Any illness acquired from food
Includes food infection, food poisoning
What is food infection/food-associated infection?
Pathogen colonizes/multiplies within the GIT
I.e. E.coli, salmonella
What is food poisoning/food intoxication?
Associated with toxin production by pathogen
Does not always require the presence of viable pathogen (i.e. improperly cooked/stored food)
i.e. C. botulinum, S. aureus
What do bacterial GI infections cause and are typically acquired?
Typically acquired from food and cause both food infection and food intoxication (many associated with an enterotoxin)
What is the pattern of a bacterial infection?
Fluid and electrolyte secretion may be a function of enterotoxin
Invasive pathogens may cause damage to intestinal epithelium (bleeding, perforation, ruffling of epithelial cells in the GIT)
Activation of TLRs (associated chronic inflammation eg Crohn’s), NLRs leads to intestinal inflammation
What is the pattern of a viral infection?
Generally cause food infection (some viruses produce potent viral enterotoxins)
May be acquired from food or infected individuals (highly transmissible)
Activation of multiple pattern recognition receptors associated with intestinal inflammation
What is the pattern of a parasitic infection?
Generally cause food infection
Most have limited distribution: associated poor hygiene/water sanitation etc
May be acquired from food/water
Activation of complement, eosinophils (inflammation)
Internalization of host cells in the intestinal lining may lead to damage, blood sucking from the intestine may lead to nutrient deficiency and anemia
Parasitic infections generally associated with Th2 adaptive immune response
What are the clinical symptoms of a GI infection?
Most mild GI infections require only management of symptoms
Fluid and electrolyte replacement
Nutritional replacement
Probiotics
What type of infection is a stool sample valuable for?
Generally for parasitic infection (macroscopic, microscopic)
Stool cultures may be used for prolonged/severe bacterial infections
What are some quantitative methods for the diagnosis of GI infections?
Serological analysis (PCR, ELISA) Not super accessible?
What is the treatment of GI infections?
Antibiotics not generally recommended (restoration flora important)
Macrolide abx for severe bacterial infection
Metronidazole broad spectrum abx/antiparasitic
Anti-emetic anti-mortality drugs, electrolyte and fluid replacement as necessary
What vaccinations to GI infections are there?
Rotavirus Cholera Traveller's diarrhea (ETEC) Hep A Barriers to immunization??
DDx considerations
For similar infections consider
Age
Immune status
Source of transmission - food water nosocomial
Prevalence of candidate infections in a given location
Extra-intestinal symptoms
Incubation period and length of symptoms
When are precise diagnoses for infectious disease of the GIT crucial?
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